A capping machine or conventional capping apparatus includes a star wheel rotatable about a machine axis and having a plurality of outwardly opening pockets adapted to receive bottles fed in an assembly line fashion to the star wheel. Overlying the rotating star wheel is a plurality of individual capper heads for use in applying a cap to the upper threaded neck of a plastic bottle carried by the star wheel in an arcuate or circular path centered about the machine axis. A turret rotates the star wheel and capping heads in synchronism about the machine axis with an individual capping head located directly above each bottle receiving pocket on the star wheel. The capper heads employ a clutch mechanism whereby the head carrying a cap is rotated and driven axially downwardly at a predetermined force and torque limiting value to tighten the cap onto the bottle neck.
In accordance with standard practice, an entrant guide mechanism or conveyor is mated with the capper star wheel to feed filled bottles to an entry point on or at the end of the path of movement of the capper star wheel. An exit guide mechanism or conveyor is similarly mated to the capper star wheel to transfer the capped bottles from an exit point on or at the end of the rotating capper star wheel. A stationary rear guide plate extends generally between the entry and exit points on the capping machine and is spaced radially outwardly from the pockets of the star wheel and functions to retain the bottles in the pockets as the star wheel rotates in unison with the capping heads. Below the bottles or containers is a segmented ring, known as a wear plate, rotated with the star wheel onto which the bottles or containers rest during capping. This is a conventional capping machine employed in bottling plants and is the mechanism to which the present invention is directed.
During the capping operation, it is necessary to assure that the bottle does not spin as the cap is tightened. A spinning action during the capping procedure can cause damage to the plastic container and reduce the desired tightness of the cap being applied automatically to the bottle as it is translated in a path determined by the star wheel. In the past, certain cap designs required a relatively high downward force during the capping operation. When this occurs, spinning of the bottle is prevented by frictional contact with the pocket, with the rear guide plate or with both of these structures. As the downward force during the capping operation has been reduced due to the design and functional characteristics of the cap being applied, friction at the neck of the bottles has been increased either by the use of upwardly directed knife ridges provided in the anti-spin segment on the top of the individual star wheel pockets. This structure is disclosed in Peronek U.S. Pat. No. 4,939,890. The knife ridges on the anti-spin segment on each pocket engage the lower surface of a circular flange at the bottom of the threaded neck of a plastic bottle to prevent rotation of the plastic bottle. The use of knife ridges to prevent bottle rotation is more effective than using a downward force on the bottle. For that reason, the anti-rotation or anti-spin device of Peronek U.S. Pat. No. 4,939,890 has become the standard in the trade to prevent rotation of plastic bottles as they are being capped with relatively low downward force. Peronek U.S. Pat. No. 4,939,890 teaches a mechanism for externally applying a downward force on the body of a bottle being capped, which force is independent of the downward force created by the capping operation. This anti-spin or anti-rotation mechanism has been successful; however, it requires a mechanism for exerting a downward force on the bottle which is expensive and is dependent upon certain structural characteristics at the upper portion of the bottle itself. Changes in bottle configuration often require a new force exerting mechanism.
The anti-rotation device of Peronek U.S. Pat. No. 4,939,890 is a successful arrangement for applying plastic threaded safety caps onto the top of plastic bottles where the caps do not require heat to set or position the lower lock band around the neck of the bottle. The lock band of the cap simply snaps into a locking position when the capping head threads the cap onto the upper threaded neck of the plastic bottle. In this type of capping operation, the capper head exerts a downward force of between 15–20 pounds. This low axial force makes retention of the bottle from rotation within the star wheel pocket very difficult. This situation motivated the development and use of the anti-rotation feature disclosed and claimed in Peronek U.S. Pat. No. 4,939,890. Although Peronek U.S. Pat. No. 4,939,890 successfully prevents bottle rotation during the capping process, the knife ridges leaves a mark on the lower lip of the plastic bottle. In addition, the knife ridges causes small amounts of plastic to be scratched off the bottle. Over time, these plastic scraps accumulate and must be removed from the bottle capping machine, thus resulting is down time for the machine.
An alternative bottle capping arrangement is disclosed in Martin U.S. Pat. No. 5,826,400 and sold by AMCO Products Company under the trademark PETA DRIVE. In this device, plastic bottles with pedaloid bases are capped in a standard machine with a lower plate rotated with the capping heads. The lower plate includes nests having recessed bottle supporting surfaces, which nests are directly aligned with the capping heads and pockets of the rotating star wheel. In this device, a plurality of specially contoured recesses that match the pedaloid base configuration are used to receive and support the bases of the bottles as the bottles are moved by the star wheel. Since the bottles rest upon the recessed bottle supporting surfaces and are held within the nest on the plate, rotation of the bottles is prevented by an interference between the fingers in the nest and the bottom, or base, of the bottle. This bottle capping arrangement, does not use knife ridges to prevent bottle rotation during the capping operation. However, the provision of a lower circular wear plate with machined recesses, each matching the contour of a pedaloid base of the plastic bottles, is quite expensive. Each of the contoured recesses must be specially produced and accurately matched with respect to the actual shape of each pedaloid base of the bottle being processed. Consequently, each bottle requires its own lower support wear plate. Indeed, when the filled bottles being capped are changed from a four pad pedaloid base to a five pad pedaloid base, a completely new, specially machined plate for supporting the pedaloid bases must be assembled onto the machine. This arrangement for providing a plate rotatable with the star wheel for supporting the lower pedaloid bases of the bottles demands a plate which must be accurately machined for use with specific star wheels.
Another anti-rotation system includes arrangement for fixing the support member or wear plate in a position spaced from the turret where the containers are supported by the rib and slide along a rib as the container is moved around the arcuate path dictated by the movement of capping head and the star wheel. The rib extends into the lower recess of the pedaloid base of the individual bottle to prevent rotation of the bottle or container as the capping head drives the cap downwardly onto the upper threaded neck of the bottle. By using this construction, a lower support plate carrying the upstanding rib is fixed and does not rotate with the star wheel. This use of a fixed rib constitutes an improvement over other arrangements for using a lower plate with specially contoured recesses to provide interference against rotation of the bottle by the capping head; however, it requires a significant modification of the capping machine. Furthermore, the position of the rib relative to the start wheel must be adjusted for different number pedaloid bases. The repositioning requires the exchanging of one rib with another rib having a different curvature. This involves expensive retrofitting.
Still another anti-rotation system is disclosed in Peronek U.S. Pat. No. 5,934,042. In this system, plastic bottles with pedaloid bases are capped in a standard machine with a lower wear plate rotated with the capping heads. The wear plate includes nests that have bar-like abutments that are positioned on the surface of the wear plate. During the capping operation, the base of the bottle is lowered onto the bar-like abutments. These bar-like abutments engage the bottom surfaces of the pedaloid base to prevent the bottle from rotating during the capping operation. The bar-like abutments are designed to be removable and adjustable so as to accommodate different sizes and types of bottles. This bottle capping device is a significant improvement over prior bottle capping arrangements in that there is very little cost associated with adjusting the bar-like abutments on the wear plate to accommodate different types of bottles to be capped. In addition, Peronek U.S. Pat. No. 5,934,042 discloses an anti-rotation mechanism to be used on a capping machine which does not rely upon developing large downward frictional forces on the top of the bottle during the capping operation.
Although Peronek U.S. Pat. No. 5,934,042 is a significant improvement over prior bottle capping arrangements, bottles that are capped by the bottle capping device of Peronek U.S. Pat. No. 5,934,042 may be deformed or crushed during the capping process. This deformation or crushing problem primarily exists when capping plastic bottles. Prior to a plastic bottle being capped, the bottle is filled with a liquid. Commonly, the bottle is filled with a heated liquid prior to being capped. The heated liquid in the plastic bottle tends to soften the plastic bottle thereby making the bottle susceptible to deformation. During the capping operation, the capper heads are lowered onto the neck of the bottle apply a downward force while screwing a cap onto the neck of the bottle. Due to the softened state of the plastic bottle, this downward force can cause the body and/or base of the plastic bottle to deform or be crushed during the capping operation.
The incidents of deformation or crushing are especially evident when using the bottle capping machine of Martin U.S. Pat. No. 5,826,400 and in bottle capping machines wherein a large downward force is used to prevent the bottle from rotating. In the bottle capping machine of Martin '400, the base of the bottle rests upon a bottle supporting surface. As a result, when a downward force is applied to the softened plastic bottle, the body and/or base tends to deform or crush since the base of the bottle cannot move downwardly. The incidence of deformation or crushing when using the bottle capping machine of Peronek U.S. Pat. No. 5,934,042 is much less than in Martin U.S. Pat. No. 5,826,400 since the base of the plastic bottle rests on the bar-like abutments and not the top surface of the wear plate. As a result, the base of the bottle can move downwardly some small distance when the cap is applied to the bottle thereby significantly reducing the incidence of deformation or crushing of the body and/or base of the bottle during the capping process.
In view of the existing art of capping plastic bottles, there is a need for a bottle capping device than can prevent the bottle from rotating during the capping process without causing the bottle to be deformed or crushed.